In recent years, probiotics preparations using Lactobacillus, Bifidobacterium and the like haying high lactic acid producing ability have been reported (Patent Reference 1) and many of them have been on the market. Basic function of the preparations is regulating the functions of the intestine. When a host ingests the preparations, pH in the intestinal tract is lowered due to the lactic acid produced by a lactic acid producing strain included in the preparations. Accordingly, it is considered that the number of unfavorable bacteria which cannot grow under such a low pH environment is reduced, and the regulation of intestinal functions is shown as a result thereof. The general idea as the probiotics which brings effects such as health improvement and disease resistance to the hosts by such a microbial function is broadly accepted socially, and the effects have been also recognized. The probiotics according to the present invention means a viable microorganism which show useful activities upon the health of animals and humans.
Further recently, it has been reported not only on the lactic acid produced by the lactic acid bacteria, but also on the fact that the lactic acid bacteria has the immunostimulating activity to host by peptidoglycan and the like proteins which are contained in the provided microbial cells themselves and bacteriocin which shows a narrow range of antibacterial activity for certain specific bacteria (Non-patent reference 1).
Additionally, short-chain fatty acids produced by the enteric fermentation in humans and animals have been drawn attention. With regard to the short-chain fatty acids, their function which lowers pH in the intestinal tract, effects which accelerate movement of intestine (Non-patent reference 2), and accelerate absorption of Na and the like have been shown. Among the short-chain fatty acids, butyric acid is particularly drawing attention. As its functions, it has been shown that it is important as an energy source of colon epithelial cells (Non-patent reference 3) and that it brings very useful effects for hosts, such as its anticancer activity (Non-patent reference 4) and its effect to accelerate differentiation of intestinal mucosa cells.
However, there is a problem in view of its characteristic odor and safety when butyric acid is directly and orally administered. Thus, it seems to be effective to produce it in the intestine in a small amount and to carry out its continuous absorption in host, rather than its direct oral administration, in order to allow such an important physiological active substance to act on a host more effectively.
As an accelerator of entericbutyric acid concentration which uses a microorganism, those which use cells of Lactobacillus acidophilus and/or Bifidobacterium longum as an active ingredient have been disclosed (Patent Reference 2). However, there is no description in the document on their effect regarding actual diseases, and the degree of disease resistance due to administration of the cells is unclear.
Also, a method has been disclosed, which uses Clostridium butyricum (to be referred also to as C. butyricum hereinafter) as the microorganism having ability of producing butyric acid (Non-patent Reference 5). According to such an already known reference, the Clostridium butyricum which is already put on the market as a butyric acid producing bacterium has the regulation of the functions of intestines. However, regarding its effect for inhibiting precancerous lesion cells, there is a problem that effect by the microorganism alone is low, since it is necessary to administer it together with a special substrate in order to obtain sufficient effect (Non-patent Reference 6). Also, as a result of the investigation of preventive effect on inflammatory bowel disease carried out in the same manner, there is a problem that the effect by the microorganism alone is low.
Additionally, these references do not clearly describe an illustrative method which uses Butyrivibrio fibrisolvens as a probiotics, and its effects are not revealed therein, too.
Based on the above, great concern has been directed toward a bacterial strain which has a high disease resistant activity due to having further high health improving, anticancer and immunostimulating functions for a host and also has the ability to produce butyric acid,    Patent Reference 1: JP-A-2002-306125    Patent Reference 2: JP-A-10-84909    Non-patent Reference 1: Kawai Y et al., Curr. Protein. Pept. Sci., 2004, 5(5), 393-8, “The circular bacteriocins gassericin A and circulacin A”    Non-patent Reference 2: Cherbut, C. et al., American Journal of Physiology, 1998, 275, G1415-G1422, “Short-chain fatty acids modify colonic motility through nerves and polypeptide YY release in the rat”    Non-patent Reference 3: Cummings, J. H., Gut, 1981, 22, 763-779, “Short-chain fatty acids in the human colon”    Non-patent Reference 4 Hague, A. et al., Gastroenterology, 1997, 112, 1036-1040, “Butyrate acts as a survival factor for colonic epithelial cells: further fuel for the in vivo versus in vitro debate”    Non-patent Reference 5: Kanauchi O. et al., Curr. Pharm. Des., 2003, 9(4), 333-346, “Modification of intestinal flora in the treatment of inflammatory bowel disease”    Non-patent Reference 6: Nakanishi S. et al., Microbiol. Immunol., 2003, 47(12), 951-958, “Effects of high amylose maize starch and Clostridium butyricum on metabolism in colonic microbiota and formation of azoxymethane-induced aberrant crypt foci in the rat colon”.